Energy from the Sun is the source of energy for nearly all life on Earth.
plants use a small percentage of light energy from the Sun to make food during photosythesis. This energy then works its way through the food chains as animals eat the plants and each other.
Energy lost at each stage is used for staying alive, e.g in respiration, which powers all life processes.
Most of this energy is eventually lost to the surroundings as heat. This is especially true for mammals and birds whose bodies must be kept at a constant temperature which is normally higher than their surroundings.
Material and energy are also lost from the food chain as waste products. Egestion is when food that cant be digested passes out as faeces. Excretion is when the waste products of bodily processes are released
Waste products and uneaten parts, e.g bones, can become starting points for other food chains.